Disc brakes



United States Patent FOREIGN PATENTS [72] Inventor RoyCampbell Dudley,England X U A 2 7 W 6 l m a l m C n d mww mmr am n e m :w t w E Fl w e er m m G ma P m u 9 Wm HMV 2 MM MS a E d 9 mm M mw t PA 0 n m m a m 90 m7m? 99L l glm mnu nfi 1. nm Wfimk k 7FDGaB 0 e d P .1 pmmmx AFPA 111]]1253 2247 [iii .m m m w ahuw e. .m .m n a i s .m m a CD0 h e h tABSTRACT: In a disc brake ofthe kind com ry housing, axially spacedbrakin shaft extending axially within brake discs slidably keyed on saidshaft for engagement with a h mwa maeu CSH a D. d W mw 838mm phat r P nm fl mfi .m mfi m e i m m e 0 en t 05 O df wmmmm wim fl n mmm i ,d O C ae r .l e nl mm t t P m m m p i o S D-SH mS.l GOWV, WCD- f a m b mmm f mo C 5 amfiw MCCC srmhemp 04 Hm 1 0 8 2F 8 8" cum m u .l. F" m m al u Wmm fi m m K W m A m m RS Bm L cm w C ECS m D/DU I l. 1 4 2 1 5 5 5 rr .l..i

tion of the brake, and a plurality of angularly spaced pilot lugsextending radially inwards from said housing for centralizing saidpressure plates with respect to the axis of the brake, an insert ismounted for rocking movement in the radially innermost face ofat leastone pilot lug and is adapted to be engaged by one or both pressureplates in the application ofthe brake.

X X 7 My w 29 S 71 2 m 7 l6 8 8 1 SW m N mm w m n... w mm m wT n e 6FTWA. m m DW m R E a 6 a N 6 e Um S f 3 o M .m B F O 9 l. l 3 0 6 2 U U3 Patented Dec. 1, 1970 Sheet l of 2 DISC BRAKES This invention relatesto improvements in disc brakes of the kind in which relativelystationary and rotatable surfaces are brought into frictional engagementby axial separation of a pair of cooperating pressure plates betweenwhich are arranged angularly spaced balls working in complementaryinclined recesses in the adjacent surfaces of the plates, theapplication of the brake being initiated by moving the plates angularlyin opposite directions.

In the usual brake of this kind the rotatable surfaces are formed by oron discs splined or otherwise keyed for axial sliding movement on arotatable shaft, and the stationary surfaces are formed by the end wallsof a housing enclosing the discs and pressure plates.

The pressure plates are centralized by angularly spaced pilot lugsprojecting inwardly from the housing, and after the initial angularmovement of the pressure plates in opposite directions the plates arecarried round with the rotating discs until a projecting lug on oneplate engages an abutment face on a pilot lug which arrests its movementwhile the other plate continues to move angularly whereby the plates areurged apart in an axial direction to apply the brake.

With this type of brake it has been found that in the application of thebrake the force applied to the actuator by which the initial angularmovement of the pressure plates in opposite directions is effected hasto be built up to a certain value before the pressure plates slideangularly over a pilot lug and start the servoaction of the pressureplates.

It is believed that this effect is probably due to the fact that withtolerance variations part of the periphery or crown portion ofa pressureplate is of greater radius than the edge of the pilot lug with which itfirst engages so that the plate has to move transversely away from thelug before it can clear that edge.

According to our invention the difficulty referred to above is overcomeor at least its effect is materially reduced by providing in theradially innermost face of at least one pilot lug an insert with whichthe peripheral edge of a pressure plate or each pressure plate isadapted to engage in the application of the brake and which is somounted in the pilot lug that it is free to aline itself automaticallywith the periphery of the pressure plate.

The insert is conveniently mounted in a part-circular or part-sphericalrecess in the radially innermost face of the pilot lug in which it canrock, the insert having a complementary arcuate or part-spherical facecooperating with the recess and a substantially flat face for engagementby a pressure plate or by both pressure plates.

Normally only one of the pressure plates is in sliding engagement withthe insert in the pilot lug, this being the plate which continues itsangular movement after the other or stationary plate has been arrestedand provides the servoaction, but in some constructions the stationaryplate or both plates may be in engagement with the insert.

One practical embodiment of our invention is illustrated by way ofexample in the accompanying drawings in which:

FIG. 1 is an end view ofa brake of the kind set forth with the end coverof the housing removed;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is a rear view of an enlarged scale of an insert for a pilot lug;and

FIG. 4 is a corresponding section of the insert on the line 4-4 of FIG.3.

In the brake illustrated is the stationary brake housing. A rotatableshaft 11 extends axially through the housing, and within the housing twobrake discs 12, 13 are splined on the shaft for axial sliding movementthereon. Each disc carries rings 14 of friction material on each of itsfaces. The discs are adapted to be urged apart to bring them intoengagement with radial surfaces on the stationary housing. One surface15 is formed on the integral end wall 16 of the housing and the other isformed on a detachable cover or end plate (not shown) for the other endof the housing. The separation ofthe discs is effected by twocooperating pressure plates 17, 18 located between the discs. Balls 19are located in complementary inclined recesses 21 in the adjacent facesof the pressure plates so that on relative angular movement between theplates they are urged apart'to force the brake discs into engagementwith the stationary braking surfaces on the housing.

The pressure plates are centralized by three angularly spaced pilot lugs22, 23, 24 which project radially inwardly from the peripheral wall ofthe housing.

The application of the brake is initiated by moving the pressure platesangularly in opposite directions. This is effected by a pull on anactuating rod 25 pivotally connected to a pin 26 coupling together theinner ends of two toggle links 27, 28 of which the outer ends arepivotally connected to radially projecting lugs 29, 31 on the respectivepressure plates.

The frictional engagement of the pressure plates with the brake discscauses the plates to be carried round with the discs until, depending onthe direction of rotation of the discs, at stop lug 32 on the plate 17engages the pilot lug 22. or a stop lug 33 on the plate 18 engages thepilot lug 23. Further angular movement of one pressure plate is thusarrested while angular movement of the other pressure plate continuesand a servoaction is produced which applies the brake.

This is a well-known type of brake.

Normally the radially innermost faces of the pilot lugs are partcylindrical, being parts ofa cylindrical surface of a diameter slightlygreater than the diameter of the pressure plates.

According to our invention a part-circular recess 34 is milled in theradially innermost surface of at least one of the lugs, in this case thelug 23. The recess has located in it an insert 35 having an arcuateouter face of the same radius as the bottom of the recess and a flat orsubstantially flat inner face for engagement by the peripheral edge ofapressure plate.

As the insert is free to rock in the recess 34 it can automaticallyaline itself with the portion of the periphery of the pressure platewhich engages it, whatever may be the radius of that portion withtolerance variations.

The ends of the insert 35 may be chamfered off as shown at 36 in FIG. 4and the circumferential length of the insert between the chamfered endsis less than the minimum spacing in a circumferential direction betweenthe adjacent parts of the opposed faces of the pilot lug to ensure thatno abutment loads can be taken by the insert.

The arcuate outer face of the insert may have a central flat as shown at37 in FIG. 4 so that only the parts 38 adjacent to opposite ends are inangular sliding engagement with the partcircular bottom of the recess 34in the pilot lug.

The length of the insert in the direction of the axis of the brake maybe such that it can be engaged by both pressure plates or by only one ofthe pressure plates.

In a modification the recess in the pilot lug may be part spherical inwhich case the radially outer face ofthe insert will be of complementarycontour.

In the drawings an insert is shown only in the pilot lug 23 but asimilar insert may be provided in the lug 22, the lugs 22 and 23 beingthose adjacent to the actuating means 25, 27, 28 by which the pressureplates are moved angularly in opposite directions to initiate theapplication of the brake.

The pilot lug 23 is the one which is first engaged by a pressure plateor by both pressure plates in the normal direction of rotation of thebrake discs while the pilot lug 22 is the one which is first engagedwhen the discs are rotating in the reverse direction.

The insert may be formed of any suitable material. Preferably it isformed of a metal or alloy having a low coefficient of friction so thatfrictional resistance to movement of a pressure plate relative to theinsert is reduced to a minimum. Alternatively the insert can be made ofavery hard material so that any wear which takes place is on the pressureplate or plates rather than on the insert.

Iclaim:

l. A disc brake comprising a stationary housing. axially spaced brakingsurfaces in the housing, a shaft extending axially within the housing,axially spaced brake discs slidably keyed on said shaft for engagementwith said brake surfaces in the housing, cooperating pressure plateslocated between said brake discs, angularly spaced balls located incomplementary inclined recesses in the adjacent faces of said pressureplates, means for moving said pressure plates angularly in oppositedirections to initiate the application of the brake, and a plurality ofangularly spaced pilot lugs extending radially inwards from said housingfor centralizing said pressure plates with respect to the axis of thebrake, wherein the improvement comprises a self-alining insert mountedfor rocking movement in the radially innermost face of at least one ofsaid pilot lugs and adapted to be engaged by one or both pressure platesin the application of the brake,said insert having a substantially flatradially innermost face tangentially engageable by a pressure plate,said pilot lug having a part-circular recess in its radially innermostface to receive the radially outermost face of said insert, saidoutermost face being arcuate and of substantially the same radius assaid recess so that said insert is rockable within said recess.

2. A disc brake as in claim 1, wherein the radially outermost facecomprises a substantially flat central portion between two arcuateportions of substantially the same radius as the recess in which it ismounted,

3. A disc brake as in claim 1, wherein the recess is part spherical andthe radially outermost face of the insert is part spherical and of thesame radius as the recess.

4. A disc brake as in claim 1, wherein the ends of the insert arechamfered and the overall length of the insert in a circumferentialdirection is less than that of the adjacent part of the pilot lug inwhich it is mounted.

5. A disc brake as in claim 1, wherein the insert is formed of a metalor alloy having a low coefficient of friction.

6, A disc brake as in claim 1, wherein an insert is mounted in each oftwo pilot lugs with which a pressure plate or each pressure plate firstengages when the brake discs are rotating in the normal forwarddirection and in the reverse direction respectively.

